Engines, including diesel engines, gasoline engines, gaseous fuel powered engines, and other engines known in the art exhaust a complex mixture of air pollutants. These air pollutants can include gaseous compounds, such as the oxides of nitrogen, and solid material known as particulate matter or soot. Due to increased attention on the environment, exhaust emission standards have become more stringent and the amount of gaseous compounds and solid material emitted from an engine is regulated depending on the type of engine, size of engine, and/or class of engine.
One method implemented by engine manufacturers to comply with the regulation of pollutants exhausted to the environment has been to reduce, convert, or otherwise remove the gaseous compounds and particulate matter from the exhaust flow of an engine with catalysts and filters. These devices, however, may only function efficiently under particular operating conditions. For example, some catalysts function efficiently only when exposed to elevated temperatures. Particulate filters function for only a period of time, until they become saturated with soot. In order for the particulate filters to continue operation, they may need to be heated above a combustion threshold of the trapped particulate matter such that the particulate matter is burned away. Accordingly, some engine exhaust systems are equipped with means for artificially raising a temperature of the exhaust passing through the catalysts and filters, such that use of these devices can be improved and maintained.
An exemplary exhaust system that artificially raises the temperature of exhaust passing through a filter is disclosed in U.S. Patent Publication 2012/0003131 of Ibrahim et al. that published on Jan. 5, 2012 (“the '131 publication”). Specifically, the '131 patent discloses an electric power system having a diesel engine connected to drive a generator via a mechanical coupling. The generator, in turn, produces electric power used to propel a locomotive. An electric load bank is used to dissipate excess power produced by the locomotive during braking. An electric heater is provided and includes resistive elements located within an exhaust flow of the engine. The electric heater is used to raise a temperature of exhaust from the diesel engine up to about 1000° F., at which soot trapped in an exhaust particulate trap is oxidized. An external power source, the generator, and/or the excess power produced during braking is used to power the electric heater.
Although the system of the '131 publication may adequately function to regenerate an exhaust particular trap, it may still be less than optimal. Specifically, the system may not consider important operating conditions of the diesel engine during regeneration that could improve an efficiency of the regeneration process. In addition, the electric heater, by itself, may be insufficient to adequately oxidize the trapped particulate matter.
The disclosed system and method address one or more of the problems discussed above and/or other problems of the prior art.